Fence charger controller circuit



' 1956 I 1. L. HURST, JR., ETAL 2,767,331

FENCE CHARGER CONTROLLER CIRCUIT Filed Nov. 25, 1952 .ITZ FEfiTLIZ-LELeonard L. HumszJr' United States Patent FENCE CHARGER CONTROLLERCIRCUIT Leonard L. Hurst, Jr., and Ernest K. Hudson, Caldwell, Idaho,assignors to International Electric Fence (30., Inc., Caldwell, Idaho, acorporation of Washington Application November 25, 1952, Serial No.322,420

11 Claims. (Cl. 307132) This invention relates to electric fences and,more particularly, to a fence charger for supplying controlled electricimpulses to a fence wire or the like.

Electric fences have been widely accepted as effective enclosures forcattle and stock of many varieties. They pose the hazard of shockinghumans and the more susceptible animals injuriously, or even fatally.Accordingly, codes setting forth safe practices under varying conditionshave been promulgated and compliance with these is a requisite to afence charger. Thus, the maximum voltage and current on the enclosurewire, the charge period, and the repetition rate must be restricted andcontrolled by the fence charger. Furthermore, a possible failure of theimpulse forming section of the fence charger must not resutt inapplication of a prolonged charge to the enclosure wire, lest an animalin contact with the wire be paralyzed.

In addition to the safety problem there exist the problems of achievinglong-lived .and e'fficient operation. To this end simple, long-wearingmechanical parts are desirably employed, together with such standardelectrical elements as have a rugged, long-wearing characteristic. Formost efficient and convenient operation, the electric fence should beenergized from an alternating current source without rectification ofthe current. Provision of indicators to show continuing operation of thecharger and to Warn of excessive loads or short circuits on the wire isalso desirable to insure early restoration of the device to aneiiicien't operating condition.

Accordingly, it is an object of this invention to provide an improvedelectric fence system capable of efficient, safe operation over longperiods of time.

Another object is to provide an improved, safeguarded electric fencesystem which employs but a few stable, long-lived elements.

It is a further object to doubly safeguard against the dangers ofprolonged current charging by the provision of both a thermal and anelectromagnetic switch to disconnect power from the fence wire before adangerous prolongation of the charge may occur.

Another object of this invention is to provide a control for limitingthe duration of the electric pulses with which the electric fence ischarged and, further, to arrange a time-control element of such controlfor visually indicating the intermittent operation of the fence charger.

Yet a further object of this invention is the provision of a glow lampvisual indicator to give a warning upon the occurrence of an excessiveload upon the output circuit.

Other and further objects and advantages of this invention will bereadily perceived and may best be understood by reference to thefollowing description, taken in conjunction with the accompanyingdrawing, in which:

The single figure shown is a schematic representation of the circuit andelements of an electric fence system embodying the present invention.

Using numerals to designate the illustrated and described parts, we haveprovided an electric fence system ice comprising a fence charger 10having power input terminals 11 and charge output terminals 12, a chargeconducting fence wire 13 connected to one of the output terminals and agrounding return conductor 14 connected to the other output terminal.The input terminals 11 may suitably be connected to a source ofelectrical power, preferably a steady alternating current source, toenergize the fence charger 10 so that it may supply alternatingelectrical impulses for the fence wire 13. It will be understood that,in lieu of the fence wire, other electric shock conductors employed tocontrol or shock living organisms might be substituted, as such arewithin the true scope and spirit of the present invention. The chargedconductor will generally be insulated from the ground, with which thegrounding conductor 14 provides a return path for current. Thus, theoutput circuit is generally open and transmits current only when thecharged wire is grounded, as through contact with livestock or the like.

To interrupt current received at the input terminals 11 and to convertit into a train of electrical impulses, the fence charger 10 comprises acyclic thermal current interrupting device 15 serving as a chopper orflasher device in the line of current transmission to the load. Thisdevice includes a pair of temperature responsive bimetallic switch arms16 and 17 connected together and conductive of electricity. The lessresponsive arm 16 supports one of a pair of normally closed switchcontacts 18, While the more responsive or thermally sensitive arm 17supports one of a pair of normally open switch contacts 19. Thesecontacts 18 and 19 are composed of long-wearing alloys of a type thatwill minimize pitting and sticking, since the normally closed contacts18 operate as breaker points and the normally open contacts 19 have 'animportant safety function.

An electrical resistance heater 20 is connected to the arm 16 for thereception of current through the normally closed contacts 18. Thisheater 20 is arranged to transmit su'fiicient heat to the bimetallic arm16 to cause opening of the contacts 18 after a predetermined period ofclosure. The heater and the arm 16 are further designed to cool at asuflicient rate that the contacts 18 will close again after apredetermined quiescent or off period of the charger.

During a cyclic repetition of heating and cooling of the arm 16,su'fiicientheat will be received and retained by the bimetallic arm 17to cause the normally open contacts 19 to remain closed. Should theheater 20 burn out or otherwise cease to function, the contacts 19 willopen to deenergize the remainder of the fence charger. For the sake ofsafety, then, the contacts 19 open when the closed contacts 18 are nolonger opened by automatic thermal actuation. During normal cyclicoperation, however, electric impulses are transmitted at a predeterminedrate of repetition by the interrupter device 15. Conveniently, a manualswitch 21 is interposed in the line 22-23 between the input terminals 11and the device 15.

While the interrupter device may be designed to determine not only therepetition rate but also the duration of each electric impulse, a moreaccurate and de sirable control of the impulse duration is achievedthrough operation of a time delay relay 25. This relay includes normallyclosed contacts 26 connected in the line 22 serially with the thermalswitch contacts 18 and 19 to pass the electric impulses from the currentinterrupter section to the load. These relay contacts 25 are arranged tobe opened, after passing an electric impulse, of specified duration, bythe energizaticn of relay solenoid 27 through suitable time delay means.We prefer utilization of a positive temperature coeificient resistanceand particularly a tungsten filament incandescent lamp 30 to control thesupply of energizing current to the relay solenoid 27.

For this purpose, the lamp 3% is connected across the line 2223 inseries with a variable resistance 31, effectively.

to provide a voltage divider circuit, and the relay solenoid 27 isconnected across the lamp 30. Accordingly, by a suitable design, therelay 25 will not operate until the resistance of the lamp 3% hasincreased sufiiciently to impress upon the solenoid 27 its operatingvoltage. The desired time delay in relay operation may be secured thenby an appropriate choice of relay and voltage divider circuit elements.The time delay in opening of the relay 25 will necessarily be less thanthe closed period of the breaker contacts 13, but may be made adjustablewithin such limits by employment of the variable resistance 31. Foreconomy, resistance 31 may have a fixed value.

Besides the function of controlling the duration of electric impulsesapplied to the fence wire, this voltage divider circuit and relayprovide an added safeguard against application of an uninterruptedcharge to the fence. Thus, if the breaker contacts 18 and the safetycontacts 19 should fail to open, the relay 25 will be energized afterthe preselected time delay to open its contacts 26, thereby todisconnect the fence wire 13 from the power source. In this manner botha thermal and an electromagnetic safety device are provided, such thatfailure of either does not impair the safeguarding function of the otherand failure of both is exceedingly unlikely.

The impulse limiting section of the charger, as yet another of itsfunctions, provides a visual indication of the production of electricimpulses by the repeated glowing of the incandescent lamp 30 as eachimpulse is transmitted. Failure of the lamp to glow would indicateeither a power failure or non-closing of the safety contacts 19. If, onthe other hand, the lamp 30 glows continuously, it would be apparentthat contacts 18 and 19 had stuck in their closed position. By thissimple visual indication, then, an accurate and rapid check of thecharger operation may be made.

To increase the voltage or potential of the electric impulses formed bythe current interrupter section and the impulse limiting section, thelow voltage primary coil 34 of transformer 35 is connected across theline 22-23, and the high voltage secondary coil 36 is connected throughline 37-68 to the output terminals 12. In this output circuit, a currentlimiting resistance 40 may be selectively connected by manual switch 41to reduce the potency of shocks imposed upon animals contacting thefence.

To provide a further indication of the condition of our electric fencesystem, a neon glow lamp 45 is serially connected in the output circuitand is bridged or shunted by a resistance 46 so as to glow when theoutput circuit is completed. If stock should ground the charged fencewire 13, for example, the intermittent charging current flowing throughthe resistance 46 would produce a voltage drop which, by suitabledesign, would intermittently ignite the glow lamp 45. An importantfunction of the glow lamp, however, is to indicate the impropergrounding of the fence wire by failure of insulators, contact withfallen tree limbs, and the like, so that the fault may be recognized andthe electric fence system restored to effective operation. The glow lamp.5 and the incandescent lamp 30 have the further cooperative function ofproviding a check against failure of either. Thus, when the charger ison and the output circuit is intentionally closed, intermittent glowingof only one lamp would show the other lamp to be burned out.

The charger 10 is further provided with ballast condensers i) and 51grounded to the casing (not shown) and wire 14 to minimize arcing at thebreaker contacts 18, and for similar reasons ballast condenser 52 isconnected across the contacts 26.

To operate our electric fence system, a suitable shock conductive fencewire 13 and a grounding conductor 14 are connected to the respectiveoutput terminals 12, and the manual switch 21 is closed to connect thecharger with an alternating current source. The resist nce 29 then heatsthe bimetallic arms 15 and i7 nrst to close the safety contacts 19. Animpulse of alternating current passes through contacts 1.8, 19 and 25 tothe transformer 35 and induces a high voltage charge on the fence wire13. Before the heated bimetallic arm 16 can open the contacts 18, theresistance of the lamp 30 is sufficiently raised by heating to cause therelay 25 to open, thereby to terminate the current impulse and thencethe voltage charge on the fence wire. When, thereafter, the contacts 13open, the resistance 29 is cooled to reclose the contacts 35 forconduction of another impulse.

It will be apparent that the current interrupter 15 determines therepetition rate, while the relay 25 and the voltage divider delaycircuit 331 accurately determine impulse duration. At the same time, theinterrupter 35 and the relay 25 provide a double safeguard againstapplication of a prolonged charge to the fence. Moreover, the lamps 30and 45 cooperate to provide a simple visual indication of thefunctioning of the system. In attaining these advantageous features,only a relatively few elements of rugged, long-wearing character arerequired, and several of these elements have multiple functions for thesake of economy.

Although we have described our invention in connection with a preferredembodiment thereof, many variations and modifications may be resorted toby those skilled in the art without departing from the principles andspirit of our invention. All of these variations and modifications mustbe considered within the true scope and spirit of the present inventionas described and shown above and as defined by the appended claims.

We claim as our invention:

1. In an electric fence system, a fence charger comprising electricimpulse forming means cyclically operative to supply a train of electricimpulses, an open high voltage circuit charged by such impulses, relaymeans in terposed between said impulse forming means and said opencircuit for terminating such impulses, and time delay circuit meanscyclically energized by said impulses for operating said relay meansduring each impulse but after a predetermined time delay, thereby todetermine the duration of each impulse charging said open circuit 2. Inan electric fence, a fence charger comprising electric impulse formingmeans cyclically operative to supply a train of electric impulses, anopen high voltage circuit charged by such impulses, a relay havingnormally closed contacts for passing such impulses to said open circuit,and a voltage divider circuit including a positive temperaturecoeflicient resistance energized cyclically by said electric impulses toenergize said relay during the impulses but after a time delaydetermined by said resistance, thereby to open said relay contactsrepeatedly to limit the duration of each impulse.

3. In an electric fence, an output transformer, an energizing circuitfor said transformer including a cyclic current interrupter and anormally closed relay serially con necting said interrupter and saidtransformer, and a time delay circuit energized cyclically through saidcurrent interrupter to open said relay so as to limit the period ofenergization of said transformer through said interrupter.

4. In an electric fence system, a fence charger comprising a thermalcurrent interrupting device, an output transformer, and relay switchmeans connecting said interrupting device and said transformer, andincluding time delay means periodically energized by said interruptingdevice to cause said relay means to disconnect said transformer fromsaid interrupting device after current has been passed for apredetermined period.

5. In an electric fence, a fence charger comprising current interruptingmeans arranged for connection to an alternating current source, anoutput transformer, a solenoid relay having switch contacts in seriesconnection with said interrupting means and said transformer, and avoltage divider circuit periodically energized by alternating currentfrom said interrupting means, said circuit ineluding a positivetemperature coeflicient resistance bridged across said solenoid relay tofunrish an actuating voltage thereto after a predetermined time delay.

6. In an electric fence, a fence charger comprising an outputtransformer, a line for connecting said transformer to a current source,a thermal current interrupter in said line, a solenoid relay havingnormally closed contacts in said line between said interrupter and saidtransformer, and a voltage divided connected across said line forenergization through said interrupter and including positive thermalcoefficient resistance across which said solenoid relay is connected fortime delayed actuation.

7. In an electric fence system, a fence charger comprising an outputtransformer, a cyclic current interrupter to supply a train of electricimpulses to said transformer, relay means connected between saidinterrupter and said transformer for terminating each impulse, saidrelay means including a positive temperature coefficient resistive lampto delay actuation of said relay means while visually indicating eachactuation, and an output circuit connected to said transformer to becharged thereby, said circuit including a glow lamp and a resistanceconnected in parallel in said circuit to indicate passage of currenttherethrough.

8. In an electric fence system, an output transformer, a line forconnecting said transformer to an alternating current source, impulseinitiating means for cyclically connecting the current source to saidline to send an electrical impulse through said output transformer,contacts in said line to open said line to interrupt each impulse fromsaid initiating means, solenoid means operative to open said contacts,and stationary electrical timing means energized by each impulse sent bysaid initiating means to the output transformer to begin a timing cycle,said timing means controlling said solenoid means to automaticallyactuate said solenoid means and open said contacts at the end of apredetermined period and thereby limit the duration of each impulse tosaid predetermined period.

9. In an electric fence system, an output transformer, a line forconnecting said transformer to a current source, impulse initiatingmeans for cyclically connecting the current source to said line to sendan electrical impulse through said output transformer, means in saidline separate from said initiating means for interrupting each impulsefrom said initiating means, means for actuating said interrupting means,and a positive temperature coeflicient resistance connected in circuitwith said actuating means and energized by each impulse from saidinitiating means to automatically operate said actuating means at theend of a predetermined period to actuate said interrupting means andthereby limit the duration of each impulse from said current source tosaid output transformer to said predetermined period.

10. ln an electric fence system, an output transformer, 21 line forconnecting said transformer to a current source, impulse initiatingmeans for cyclically connecting the current source to said line andoutput transformer to send an electrical impulse through said outputtransformer, electric contacts in said line for interrupting eachimpulse from said initiating means, solenoid means for actuating saidcontacts, and a positive temperature coefficient resistance meansconnected across said line and controlling said solenoid. means, saidresistance means being operative to actuate said solenoid means to opensaid contacts at the end of a predetermined period of energization ofthe resistance means by an impulse transmitted to the output transformerover said line, thereby limiting the duration of each impulse to saidpredetermined period.

11, In an electric fence system, an intermittent alternating currentimpulse type energizing circuit for delivering energy to a chargeconducting fence wire, an impulse limiting relay having contacts in saidenergizing circuit, said relay having a solenoid for actuating saidcontacts, and an impulse operated time delay circuit including apositive temperature coefficient resistance connected to said energizingcircuit and operative upon energization of said energizing circuit toactuate said solenoid after a predetermined heating period, saidsolenoid being operative upon actuation thereof to open said contacts insaid energizing circuit and thereby to interrupt delivery of energy tothe charge conducting fence wire.

References Cited in the file of this patent UNITED STATES PATENTS2,226,514 Pignolet Dec. 24, 1940 2,294,343 Nunn Aug. 2, 1942 2,294,344Nunn Aug. 2, 1942 2,316,211 Agnew et al. Apr. 13, 1942 2,398,442 MooreApr, 16, 1946

